I. Field
The present disclosure relates generally to communication, and more specifically to techniques for multiplexing data and pilot in a communication system.
II. Background
An orthogonal frequency division multiplexing (OFDM) communication system utilizes OFDM for data and pilot transmission. OFDM is a multi-carrier modulation technique that partitions the overall system bandwidth into multiple (K) orthogonal frequency subbands. These subbands are also called tones, carriers, subcarriers, bins, and frequency channels. With OFDM, each subband is associated with a respective subcarrier that may be modulated with data.
A base station in the OFDM system may transmit multiple data streams simultaneously to wireless devices. These data streams may be continuous or bursty in nature, may have fixed or variable data rates, and may use the same or different coding and modulation schemes. The base station may also transmit a pilot to assist the wireless devices perform a number of functions such as time synchronization, frequency tracking, channel estimation, and so on. A pilot is a transmission that is known a priori by both a transmitter and a receiver.
Multiplexing multiple data streams for simultaneous transmission may be challenging if these data streams are variable in nature, e.g., have data rates and/or coding and modulation schemes that change over time. The multiplexing should be such that the data streams (1) can be allocated transmission resources in sufficiently small units to reduce excess capacity and (2) can achieve frequency diversity and good performance. The pilot should be multiplexed such that good channel estimates can be obtained in different channel environments. The channel estimates are used for data detection and decoding by the wireless devices and have direct impact on performance.
There is therefore a need in the art for techniques to multiplex data and pilot in an OFDM system.